Crystallization of Poly(ethylene terephthalate) via Silica Nanoparticles Tethered with Short Diblock PEG-PET Copolymers

In this research contribution, silica nanoparticles have been synthesized and attached to low-molecular-weight diblock copolymers of polyethylene glycol (MW ≈ 200) and poly(ethylene terephthalate), MW ≈ 3500, hereafter referred to as LPPS. These nanoparticle/block-copolymer hybrid composites (i.e., LPPS) exhibit a core/shell structure and function as nucleating agents for commercial poly(ethylene terephthalate), PET. When PET contains 6 wt% of the hybrid nucleating agent, the temperature at which the maximum rate of PET crystallization occurs upon cooling from the molten state experiences a 27 °C increase, from 192 °C to 219 °C. Furthermore, 6 wt% of this hybrid nucleating agent induces an 80 °C increase in the glass transition temperature of PET, from 72 °C to 152 °C. It is proposed that hybrid nano-crystals of SiO₂ with the low-molecular-weight block copolymer most likely function as nucleation sites for PET crystallization, such that the nucleation effect of LPPS on PET induces an increase in both the crystallization temperature and the glass transition temperature. Furthermore, the elastic modulus of PET increases from 1.23 GPa to 1.74 GPa when the LPPS mass fraction is 6 wt%. The advantages of LPPS as a nucleating agent for PET are (i) its effectiveness, (ii) low cost, and (iii) ease of synthesis.